3 large (outer) celery ribs, very thinly sliced on a long diagonal (about 3 cups)

1 cup tender inner celery leaves, coarsely chopped

Preparation

Simmer water and onion in a small saucepan, uncovered, until onion is softened and most of water is evaporated, 10 to 15 minutes. Purée in a blender with vinegar, caraway seeds, sugar, mustard, and 1/2 teaspoon salt. With motor running, add oil in a slow stream and blend until dressing is emulsified.

Combine lettuce, celery, and celery leaves in a large bowl and toss with just enough dressing to coat.

Cooks' notes:
· Dressing can be made 3 days ahead and chilled in an airtight container.
· Lettuce can be washed and dried and celery can be cut 1 day ahead and chilled in sealed bags lined with paper towels.